Plat 16740 sca finding fixed

[SB-rohandhiman]

Addresses PLAT-16976, PLAT-16740, and PLAT-16763.

GitHub Actions (maze-runner.yml, python-package.yml)

• Added permissions: contents: read at top level
• Added permissions: contents: none on test-done job
• Follows least-privilege principle for workflow tokens

Django SECRET_KEY — example files (3 files)

• Replaced hardcoded keys with os.environ.get('DJANGO_SECRET_KEY', 'django-insecure-testonly')
• Falls back to a clearly marked insecure test key

Django SECRET_KEY — test fixtures (5 files)

• Replaced random-looking keys with django-insecure-testonly
• No env var needed for test fixtures

Changelog

• Added PR reference for level parameter enhancement

[SB-rohandhiman]

We have to create this PR with the next branch — we created it by mistake with master.